The present invention relates generally to mechanical bodymaker machines and in particular to metal can producing bodymaker tool packs utilizing a punch or ram to iron the cup into a can body.
In prior art drawing presses or bodymakers, the ram or punch is generally oriented horizontally such as in U.S. Pat. No. 3,496,756. In forming beverage cans, a cup is placed on the end of a punch which is then forced through a plurality of ironing rings each smaller than a previous one so that the cup is redrawn, making it thinner and longer into substantially the shape of a standard beverage can body. The '756 patent utilizes a scotch yoke type mechanism driving a piston horizontally for blanking or drawing container bodies. A disadvantage of this design structure for a bodymaker is that, in punches with longer draws, the end is cantilevered thereby allowing inertial forces and gravity to vary the uniformity of the cup wall thickness formed thereby. Gravity acts on the cantilevered end forcing the male punch closer to one side of the female die and further away to an opposite side thereby causing the cup wall thickness to be thin on one side and thick on an opposite side. It is foreseeable that the inertia of the punch itself may cause unacceptable changes in wall thickness within the tool pack.
U.S. Pat. Nos. 5,272,901 and 3,715,902 show vertical type punches operated by either a combination crankshaft/cam drive system or by hydraulic pressure. These types of presses are unbalanced and their designs do not take into consideration inertial loads or thermal stress with regard to the accuracy of the container body produced. These types of structures would create container bodies of questionable accuracy with the currently desired production levels of 400 to 600 strokes per minute with and 18 to 24 inch punch stroke length.
The present invention is directed to fill the needs and overcome the aforementioned problems associated with the mechanical bodymaker machines where it is desired to accurately control the punch while the machine is in operation by controlling and counteracting inertial and vibratory forces on the punch.